Conventionally, document output devices (e.g., computer printers and traditional print devices, for example, newspaper printing presses) have had limited ability to print grayscale image(s) and/or color image(s). To compensate, techniques, such as dithering and half toning, have been developed to allow a viewer to perceive grayscale and/or color(s) that are not native to the output device. For example, with regard to a color output device, by placing one or more red pixels in proximity to one or more blue pixels, a level of violet can be observed by a viewer. Similarly, with regard to a single color output device (e.g., computer printer equipped with black ink) by placing one or more blank (e.g., white) pixels in proximity to one or more black pixels, a level of gray can be observed by a viewer.
While achieving a more aesthetically pleasing document, these compensation techniques can present difficulty for conventional data compression systems. Noise (e.g., extraneous information such as mark(s)) can likewise reduce data compression by creating a high energy variance on an otherwise generally smooth image. Data compression reduces the space necessary to represent information. Compression can be used for any type of information. However, compression of digital information, including images, text, audio, and video is becoming more important. Typically, data compression is used with standard computer systems. However, other technologies make use of data compression, such as, but not limited to, digital and satellite television as well as cellular/digital phones.
For example, the dithering and/or half toning can be mistaken for text by a character recognition system. Further, dithering and/or half toning can lead to a document having adjacent pixels of significantly different energies (e.g., blue pixel adjacent to a red pixel) that can be difficult for a conventional document compression system to compress effectively.
Effective data compression is important for several reasons. Data compression allows information to be stored in less space than uncompressed data. As the demand for large amounts of information increases, data compression may be required to supply these large amounts of information. The size of storage devices has increased significantly; however, the demand for information has outstripped these size increases. For example, an uncompressed image can take up 5 megabytes of space whereas the same image can be compressed and take up only 2.5 megabytes of space. Additionally, data compression permits transferring of larger amounts of compressed information than uncompressed information. Even with the increase of transmission rates, such as broadband, DSL, cable modem Internet and the like, transmission limits are easily reached with uncompressed information. For example, transmission of an uncompressed image over a DSL line can take ten minutes. However, with data compression, the same image can be transmitted in about a minute.